A high electron mobility transistor (HEMT) is a field effect transistor (FET) that uses a junction between two materials that have different band gaps, different polarization, or both. One of the materials provides a non-doped channel and the other material provides carriers, such as electrons, to the non-doped channel. Channels in traditional FETs are typically doped with impurities to provide carriers. However, the carriers may be slowed down as a result of collisions with the impurities that provide the carriers. A HEMT avoids this problem by using the non-doped channel, which doesn't have the impurities. The other material provides the carriers to the non-doped channel as a thin sub-layer of highly mobile carriers in the non-doped channel adjacent to the other material. This thin sub-layer is called a two-dimensional electron gas (2DEG) sub-layer. As a result, the non-doped channel may have low resistivity to provide high electron mobility. As in the fabrication of most semiconductor devices, there is a need to fabricate HEMTs using cost effective, reliable, and simple fabrication methods.